Scissor action hoist

ABSTRACT

A scissor action hoist having at least one pair of scissor arms joining a platform with a base, and driving means for opening and closing the arms, has at least one member coupled with at least one arm to be under tension when the hoist is under load to prevent bending of that arm.

lnventor Alois Lodlge Frankfurter Weg 72, 497 Paderboen,

Germany Appl. No. 873,541 Filed Nov. 3, 1969 Patented Nov. 23, 1971 SCISSOR ACTION HOIST 7 Claims, 3 Drawing Figs.

US. Cl 187/18, l82/63, 254/122, l82/l4l Int. Cl B66b 11/04 Field of Search 187/18,

References Cited UNITED STATES PATENTS Primary Examiner- Harvey C. Hornsby Attorney-Molinare, Allegretti, Newitt & Witcoff ABSTRACT: A scissor action hoist having at least one pair of scissor arms joining a platform with a base, and driving means for opening and closing the arms, has at least one member coupled with at least one arm to be under tension when the 7 3,513,246 6/l950 Moench 254/122 hoist is underload to prevent bending ofthat arm.

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flare l'of'ye BY i scrsson ACTHON norsr CROSS-REFERENCE TO RELATED PATENT This invention concerns a scissor action hoist and is an improvement in or a modification of the invention disclosed in U.S. Pat. No. 3,558,103 issued to Alois Lodige on Jan. 26, i971 BACKGROUND OF THE INVENTION Scissor action hoists are used for many purposes, eg for loading and unloading vehicles, for bridging differences in height, for internal transportation and for feeding goods to machinery.

In the case of a hoist having a given platform size and lifting capacity it is desired, in many cases, that the lift, i.e. the distance moved by the platform, of the hoist should be as large as possible and that, when the platform is lowered, the height of the hoist should be as small as possible. The height of hoists constructed according to the Repeater Interstage Method of Lodige U.S. Pat. No. 3,558,103 amounts to about percent of their lift. Drive mechanisms can be suitably mounted between scissor arms of the hoist so that end bearings of the arms have to carry only vertical forces arising from a load on the platform of the hoist. With the dimensions described above and this method of construction the ratio of force applied by power source: lifting force of hoist will reach about 6 or 7. This ratio is always somewhat variable since a larger driving force is required to raise the hoist when the hoist is in a lowered or nearly raised position than when the hoist is approximately half raised. This arises from the fact that the effective lifting force acting on the platform increases in an approximately sinusoidal forrn with the angle made by the scissor arms and the platform whereas the vertical distance from the articulation point to the effective line of the drive mechanism does not vary sinusoidally with this angle. The drive mechanism is connected to a cross tie of one of the scissor arms and forces acting on the cross tie due to the drive mechanism tend to cause the cross tie and/or its scissor arm to bend. The dimensions chosen for the cross tie must therefore be relatively large and the length of the drive mechanism connected thereto is consequently limited. The length of the drive mechanism, which is for example a hydraulic cylinder determines the possible lift of the hoist for a given load, or for a given lift, the maximum load and thus the efficiency of the drive mechanism. This is true both for one or more single hydraulic cylinder and for two or more opposed hydraulic cylinders. X

The undercutting described in Lodige U.S. Pat. No. 3,558,l03 and the increase. in working stroke thereby achieved used with the drive mechanism arrangement in accordance with the invention, leads to an increase in the angle through which the scissor arms can be rotated. The degree of uniformity achieved in the ratio of force applied: lifting force and thus the maximum lifting force obtained depends upon the angle through which the scissor arms can be rotated. An increase in the maximum height of the the hoist can enable the ratio to reach about 7. The length of the drive mechanism must however then be larger for undercut platforms than for non undercut platforms.

In Lodige U.S. Pat. No. 3,558,103 inner scissor arms are connected together by a beam in the region of the articulation point of the scissor arms and the drive mechanisms are connected to this beam so that this beam must accept torsional forces and, when the drive mechanisms work on one side only, bending forces as well. It must therefore be of very substantial dimensions.

The point of attachment of the drive mechanism must be determined from the maximum ratio of force applied: lifting force intended in the closed position. The drive mechanism can extend only to the point where the length of the vertical from the midpoint of the beam to the line of action of the drive mechanism is equal to the radius of the beam plus the length of the piston plus clearance. The maximum achievable rotation of the scissor arms is determined by this.

By reason of these relationships, there is often difficulty in arranging the drive mechanism so as to achieve a favorable ratio of force applied lifting force or a large angle of rotation of the scissor arms for hoists of small platform length which are not undercut but especially for undercut hoists.

The hoist according to the invention of Lodige U.S. Pat. No. 3,55 8,103 can have four, three or only two scissor arms. Where there are only two scissor arms, one half of a scissor arm is subjected not only to the force caused by the drive mechanism, which is usually a tensile force, but also to a bending moment. Unless this bending moment is allowed for in the construction of the arm, it will reduce the efficiency and life of the hoist. However it is costly and difficult to construct a hoist having a scissor arm designed to take this bending moment.

SUMMARY OF THE INVENTION The invention aims to overcome or reduce these difficulties.

According to the invention there is provided a scissor action hoist comprising a base, a movable platform connected to the base by a first pair of scissor arms, a first pivot intermediate the length of the arms, corresponding ends of the arms being respectively pivoted to the base and the platform and the other ends of the arms being coupled respectively with the base and the platform to be movable therealong, driving means for raising and lowering the platform by acting between the arms, and a member coupled with one of the arms to be under tension when the platform is under load so as to counteract the tendency of that arm to bend.

According to a first embodiment of the invention the hoist also comprises a transverse beam mounted on and above one end of one of said arms, said driving means acts between the transverse beam on one side of said arm and mounting means below the pivot point at a position on the other side of said one arm member extends between the first pivot and a part of the transverse beam on said one side of said one arm to counteract bending moments imparted to the transverse beam and the scissor arms by the load on the platform and driving mechanism.

According to a second embodiment of the invention the hoist also comprises first and second transverse beams respectively adjacent the ends of one of said anus, and a second driving means, the driving means acting respectively between the transverse beams and the mounting means on opposite sides of said arms and said member extends between the first and second transverse beams on opposite sides of said one arm.

The first embodiment may also comprise a second pair of scissor arms respectively parallel with said first arms and similarly connecting the platform to the base, and a second pivot intermediate the lengths of the arms of the second pair and coaxial with said first pivot. In this case the transverse beam connects corresponding arms of each pair and a pair of said members are provided respectively connected between said beam and said mounting means.

The second embodiment may also comprise a second pair of scissor arms respectively parallel with said first arms and similarly connecting the platform to the base, and a second pivot intermediate the lengths of the arms of the second pair and coaxial with said first pivot. In this case the transverse beams connect corresponding arms of each pair.

In the first embodiment of the invention, compression and bending forces are connected directly through the member to the first pivot. The beam is thereby generally subjected to practically no bending. The beam therefor can be kept slim, thereby enabling the length of the driving means to be increased. The arms do not need to take the forces of the driving means.

In the second embodiment of the invention, the two transverse beams are directly connected by the member, which may be fixed or detachable. The member can be prestressed or constructed in such a way that, when the drive force becomes fully effective, the arms are completely relieved of load.

When the drive forces are equal to zero, the arms are compression loaded to the value of the prestress, the beams being loaded in bending in the reverse direction. The total loading of the tongs arms is reduced, however, since as soon as the drive forces= X 0, the arms are no longer subjected to the weight of the load.

Preferably the arms and the member take approximately equal parts of the drive force so that there is no bending of the arm at an angle to its central axis.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated by the accompanying drawings in which:

FIG. 1 is an end view of a scissor action hoist in accordance with the invention disclosed in Lodige U.S. Pat. No. 3,558,103 without undercutting;

FIG. 2 is a vertical cross section through a raised scissor action hoist with undercutting and opposed hydraulic cylinders; and

FIG. 3 is an end view of a scissor action hoist having only two scissor arms.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The hoists shown in FIGS. 1 and 2 comprise a platform, a base and an inner and outer scissor assembly, each assembly being formed by a completely closed scissor arm frame. The outer scissor assembly frame is formed by two outer scissor arms 3 and transverse connecting beams 4 and 5, while the inner scissor assembly frame is formed by two inner scissor arms 6 and transverse connecting beams 7 and 8 and, as shown in FIG. 1 only, a transverse connecting beam 9. The outer scissor assembly frame is attached to the base 1 by means of articulated supports or coupling 10, and bolts 11 which are supported on rails on the base by rollers, and is attached to a platform 2 by means of articulated supports 12 and bolts 13. The inner scissor assembly frame is attached to the base 1 by articulated supports 14 and bolts 15, and is attached to the platform 2 by articulated supports 16, bolts 17 and rollers or couplings frames 26. The scissor assembly frames are connected together by articulated supports 18 and 19 and bolts 20.

In FIG. 2, the bolts 20 are carried directly by the scissor arms 3 and 6. In FIG. 1 a drive mechanism 21 is connected by hinges 22, 23 to the connecting beams and 9.

Without a tension member according to the invention region 25 of the scissor arms 3 would be subjected to a tensile stress caused by the drive mechanism 21, since the line of action of the drive mechanism 21 does not lie in the same plane as the centerlines of the arms 3. The drive mechanism 21 intersects the plane defined by scissor arms 3 forming an acute angle therewith. As located, one end of the drive mechanism 21 is on a first side ofsaid plane connected to transverse beam 5 mounted on and above arms 3, and the other end of drive mechanism 5 is on the other side of said plane, connected to mounting bracket 27 which will be hereinafter described. This enables the use of a longer driving mechanism 21. Bending load on the connecting beam 5, caused by that component of the driving force which acts parallel to the center lines of the arms 3, is largely removed by a tension member 24. When the tension member-24 is present the thickness of the beam 5 may be decreased, thus leading to an improvement in the insertion of the drive mechanism 21 and so improving the efiiciency of the hoist for a given length ofscissor arms.

In the hoist shown in FIG. 2, two opposed drive mechanisms 21 according to FIG. 7 of Lodige U.S. Pat. No. 3,558,103 are incorporated.

One end of each of the drive mechanisms 21 is attached via hinges 22 either to the scissor arms 6 or to hinge arms or mounting means 27. The hinge arms 27 are arranged on both sides of the drive mechanisms 21 and are firmly connected through torsion members (not shown), corresponding to the connecting beam 9 of FIG. 1, to the scissor arms 6. The other ends of the drive mechanisms are attached via hinges 23 to the connecting beams 4 and 5. In this arrangement the tension member 24 connects the connecting beams 4 and 5. This arrangement also has the advantages mentioned above for the hoist of FIG. 1.

The hoist shown in FIG. 3 has only two scissor arms 28 and 29. The arms 28 and 29 must be connected so as to be torsion and bending resistant. The arm 29 carries the connecting beams 4 and 5 while the arm 28 carried the connecting beams 7 and 8. The scissor assembly formed by the arm 29 and the beams 4 and 5 is attached to a base (not shown) and a platform (not shown) in the same way that the outer scissor frame assembly is attached to the base 1 and platform 2 as described above with reference to FIGS. 1 and 2. The scissor assembly formed by the arm 28 and the beams 7 and 8 is attached to the same base and platform in the same way that the inner scissor frame assembly is attached to the base 1 and platform 2 as described above with reference to FIGS. 1 and 2. The articulated support 18 is attached to the arm 29. The central bolt 20 is fix welded to the support 18. The arm 28 carries the articulated support 19 to which a bearing tube 35 is welded. The drive mechanism 21 pushes through the articulated bearing 23 on the connecting beam 5.

The central bolt 20 is, in this arrangement, connected through the movable tension member 24 to the connecting beam 5. In this arrangement the tension member 24 has the effect of preventing or reducing a bending movement, caused by the driving mechanisms 21 and a load on the platform, acting on the arm 29 at an angle to its central axis. An expansion of the scissor assembly including the arm 29 as a result of elastic strain is therefore prevented or reduced, and thus a delay in movement of this assembly when the driving mechanism is operated is also prevented or reduced.

The hoist according to FIG. 3 can be undercut as shown in FIG. 2, or the angle made by the scissor arms in the lowered position can be zero as for the hoist of FIG. 1, or the angle made by the scissor arms in the lowered position may reach only approximately zero.

Iclaim:

l. A scissor action hoist comprising a base, a movable platform, a first pair of scissor arms connecting the platform to the base, a first pivot intermediate the lengths of the arms, pivot connections between corresponding ends of the arms and the base and the platform, couplings between the other ends of the arms and the base and the platform, said couplings being respectively movable along the base and the platform, driving means for raising and lowering the platform by acting between the arms, the improvement comprising a transverse beam mounted on and above one end of one of said arms, mounting means on a shaft coaxial with said first pivot point and below said one of said arms, said driving means disposed between said transverse beam above said one am and said mounting means below said one arm, and a member extending between said first pivot point and said transverse beam which is in tension when said platform is under load to thereby counteract the tendency of said arm to bend.

2. A scissor action hoist comprising a base, a movable platfonn, a first pair of scissor arms connecting the platfonn to the base, a first pivot intennediate the lengths of the arms, pivot connections between corresponding ends of the anns and the base and the platform, couplings between the other ends of the arms and the base and the platfonn, said couplings being respectively movable along the base and the platform, first and second transverse beams respectively adjacent the ends of one of said arms, a pair of driving means respectively acting between said transverse beams on opposite sides of said one arm and a member extending between said first and second transverse beams on opposite sides of said one arm which is in tension when said platform is under load to thereby counteract the tendency of said arms to bend.

3. A hoist according to claim 1, comprising a second pair of scissor arms respectively parallel with said first arms and similarly connecting the platform to the base, a second pivot intermediate the lengths of the arms of the second pair and coaxial with said first pivot, said transverse beam connecting corresponding arms of each pair, and a pair of said members respectively connected between said transverse beam and said mounting means.

4. A hoist according to claim 2, comprising a second pair of scissor arms respectively parallel with said first scissor arms and similarly connecting the platform to the base, a second pivot intermediate the lengths of the arms of the second pair and coaxial with said first pivot, said transverse beams connecting corresponding arms of each pair.

5. A hoist according to claim 1, in which the couplings and pivot connections comprise articulation support brackets and substantially rigid beams the beams being attached to the ends of the arms and carrying the support brackets, and the beams at corresponding ends of the arms resting alongside one another when the platform is lowered.

6. A hoist according to claim 1, comprising a second pair of scissor arms respectively parallel to said first scissor arms, and similarly connecting the platform to the base, a second pivot intermediate the lengths of the arms of said second pair and coaxial with said first pivot, articulation support brackets, substantially rigid beams, said brackets and substantially rigid beams forming said pivot connections and couplings, the beams being attached to the ends of the arms and carrying the support brackets, the beams at corresponding ends of the arms resting alongside one another when the platform is lowered and the transverse beam forming one of said beams, and a pair of said members respectively connected between said transverse beams and said mounting means.

7. A hoist according to claim 2, comprising a second pair of scissor arms respectively parallel to said first scissor arms, and similarly connecting the platform to the base, a second pivot intennediate the lengths of the arms of said second pair and coaxial with said first pivot, articulation support brackets, and substantially rigid beams, said brackets and substantially rigid beams forming said pivot connections and couplings, the beams being attached to the ends of the arms and carrying the support brackets, the beams at corresponding ends of the anus resting alongside one another when the platform is lowered, and the transverse beams forming two of said beams. 

1. A scissor action hoist comprising a base, a movable platform, a first pair of scissor arms connecting the platform to the base, a first pivot intermediate the lengths of the arms, pivot connections between corresponding ends of the arms and the base and the platform, couplings between the other ends of the arms and the base and the platform, said couplings being respectively movable along the base and the platform, driving means for raising and lowering the platform by acting between the arms, the improvement comprising a transverse beam mounted on and above one end of one of said arms, mounting means on a shaft coaxial with said first pivot point and below said one of said arms, said driving means disposed between said transverse beam above said one arm and said mounting means below said one arm, and a member extending between said first pivot point and said transverse bEam which is in tension when said platform is under load to thereby counteract the tendency of said arm to bend.
 2. A scissor action hoist comprising a base, a movable platform, a first pair of scissor arms connecting the platform to the base, a first pivot intermediate the lengths of the arms, pivot connections between corresponding ends of the arms and the base and the platform, couplings between the other ends of the arms and the base and the platform, said couplings being respectively movable along the base and the platform, first and second transverse beams respectively adjacent the ends of one of said arms, a pair of driving means respectively acting between said transverse beams on opposite sides of said one arm and a member extending between said first and second transverse beams on opposite sides of said one arm which is in tension when said platform is under load to thereby counteract the tendency of said arms to bend.
 3. A hoist according to claim 1, comprising a second pair of scissor arms respectively parallel with said first arms and similarly connecting the platform to the base, a second pivot intermediate the lengths of the arms of the second pair and coaxial with said first pivot, said transverse beam connecting corresponding arms of each pair, and a pair of said members respectively connected between said transverse beam and said mounting means.
 4. A hoist according to claim 2, comprising a second pair of scissor arms respectively parallel with said first scissor arms and similarly connecting the platform to the base, a second pivot intermediate the lengths of the arms of the second pair and coaxial with said first pivot, said transverse beams connecting corresponding arms of each pair.
 5. A hoist according to claim 1, in which the couplings and pivot connections comprise articulation support brackets and substantially rigid beams the beams being attached to the ends of the arms and carrying the support brackets, and the beams at corresponding ends of the arms resting alongside one another when the platform is lowered.
 6. A hoist according to claim 1, comprising a second pair of scissor arms respectively parallel to said first scissor arms, and similarly connecting the platform to the base, a second pivot intermediate the lengths of the arms of said second pair and coaxial with said first pivot, articulation support brackets, substantially rigid beams, said brackets and substantially rigid beams forming said pivot connections and couplings, the beams being attached to the ends of the arms and carrying the support brackets, the beams at corresponding ends of the arms resting alongside one another when the platform is lowered and the transverse beam forming one of said beams, and a pair of said members respectively connected between said transverse beams and said mounting means.
 7. A hoist according to claim 2, comprising a second pair of scissor arms respectively parallel to said first scissor arms, and similarly connecting the platform to the base, a second pivot intermediate the lengths of the arms of said second pair and coaxial with said first pivot, articulation support brackets, and substantially rigid beams, said brackets and substantially rigid beams forming said pivot connections and couplings, the beams being attached to the ends of the arms and carrying the support brackets, the beams at corresponding ends of the arms resting alongside one another when the platform is lowered, and the transverse beams forming two of said beams. 